Minirighi Code

- use printk() to report exceptions, instead of using kprintf()

This allows to track kernel messages via klogd, instead of bypassing it and
print messages directly to console by kprintf(). This also allows to properly
send messages to serial console, when kernel debugging to serial console is
enabled.

- set the maximum verbosity level when kernel debugging to a serial port is
enabled

- fix: move video (vga) initialization message after the main console has been
initialized to obviate a chicken/egg problem

- re-design the skel and prototypes of sys_open(), sys_close(), sys_read() and
sys_write()

- fix: correctly handle spurious IRQs

This also fixes a bug running minirighi on Bochs, that reported a lot of
messages like the following:

unhandled_interrupt(): unexepected IRQ number 007!

Bug reported by: Jon Rafkind <rafkind@...>

- fix: add an opportune suffix for the assembly instructions to specify
register size of atomic operations

- fix: missing variable declaration in lookup_chrdev() / lookup_blkdev()

/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c: In function ‘lookup_chrdev’:
/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c:109: error: ‘i’ undeclared (first use in this function)
/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c:109: error: (Each undeclared identifier is reported only once
/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c:109: error: for each function it appears in.)
/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c: In function ‘lookup_blkdev’:
/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.c:203: error: ‘i’ undeclared (first use in this function)
make[2]: *** [/home/righiandr/projects/minirighi/trunk/os/fs/vfs/vfs.o] Error 1
make[1]: *** [kernel] Error 2
make: *** [world] Error 2

- implemented functions to get/lookup structures of registered character and
block devices

struct chrdev_struct *get_chrdev(unsigned int major);
struct chrdev_struct *lookup_chrdev(const char *name);
struct blkdev_struct *get_blkdev(unsigned int major);
struct blkdev_struct *lookup_blkdev(const char *name);

added lsdev userspace application, that use the lsdev() syscall

- implemented the lsdev() system call

This system call allows to print the list of block and character devices
registered in the kernel. This can be used to debug the device manager
subsystem for now, since no block or character device are registered in the
kernel yet.